Field of the Invention
The present invention generally relates to user interfaces for electric devices, and more specifically relates to touch sensors and digitizer systems.
Description of the Related Art
A variety of different types of input devices are commonly used in a variety of different electronic systems, including computers (e.g., laptop computers, tablet computers, personal digital assistants) and communication devices (e.g., mobile phones, wireless handheld communication devices). One type of input device is generally referred to as a touch sensor or proximity sensor. A touch sensor uses a variety of different techniques to determine the position of proximate objects, such as fingers. For example, capacitive touch sensors determine the position of proximate objects by determining a change in capacitance that occurs due to the presence of proximate objects. Another type of input device is commonly referred to as a digitizer tablet, but also referred to as a graphics tablet, graphics pad, or drawing tablet. Digitizer tablets include a sensing surface upon which a user can enter input using a transducer, typically implemented as a stylus or other pen-like drawing apparatus. In typical digitizers, the transducer emits an electromagnetic signal, which is detected by the sensing surface. The electromagnetic signal detected by the sensing surface is then used and processed to determine the position of the transducer.
In general, digitizers offer increased position-detection accuracy and resolution when compared to typical touch sensors. Digitizers typically require the use of a specialized transducer for inputting. It has been desirable to combine the attributes (e.g., convenience) of touch sensors with the improved accuracy and resolution of digitizers. Unfortunately, combination touch sensor-digitizers have had limited applicability, mainly due to high cost and complexity associated with implementation, the additional three-dimensional space required to accommodate the combination, and the requirement for special types of displays that could support both touch sensing and transducer (e.g., stylus) sensing. Thus, there remains a continuing need for improved combination touch sensor and transducer-based input devices.